摘要
分析和比较了沿三条水汽输送路径降水中稳定同位素的变化。沿南方水汽路径,低纬度地区取样站降水中平均δ18O的季节差异较小。自曼谷起,降水中δ18O的季节差异明显增加。沿北方水汽路径,郑州以西取样站暖半年与冷半年平均δ18O的季节差异均大于零。随着经度的增加,降水中平均δ18O的季节差减小。沿高原水汽路径,印度次大陆南部降水中的δ18O相对较高,随着纬度的增加,降水中δ18O逐渐减小。在翻越喜马拉雅山后,由于强烈的洗涤作用,降水中δ18O急剧下降。
The variations of stable isotope in precipitation along three vapor transport path are analyzed and compared. Along the south vapor path that is from the equatorial areas through the southwest vapor passage in the Yunnan-Guizhou Plateau towards to the mid-lower reaches of the Yangtze River, the seasonal differences of mean δ18O in precipitation are small in the sampling stations located in low latitudes, but increase from Bangkok toward north. The δ18O values in precipitation fluctuate on the whole, showing the different vapor origins. The appearance of the minimum δ18O at Kunming is related to its high altitude. Along the north vapor path from west to east under westerlies, the seasonal differences of the mean δ18O in precipitation, between the warm and the cold half-year , are all greater than zero for the stations in the west of Zhengzhou, and then decrease with the increasing longitude. During the cold half-year, the mean δ18O in precipitation reaches its minimum in Urumqi with the minimum temperature, influenced by the wide Cold-High Pressure over the Mongolia, then increases with longitude gradually and keeps at a roughly same level from Zhengzhou towards east. However, the δ18O values in precipitation are lower in the east than in the west during the warm half-year, influenced by the summer monsoon o-ver East Asia markedly. Along the plateau path that is from the tropics through the Indian Subcontinent and the Himalayas to the northern Tibetan Plateau, the mean δ18O values in precipitation are correspondingly high in the south parts of the India Subcontinent, and then decrease with latitude gradually. A sharp depletion of the stable isotopic compositions in precipitation takes place due to the very strong rainout of the stable isotopic compositions in vapor in the process of the lifting on the southern slope of the Himalayas. The δ18O in precipitation is kept at a low level from Nyalam to the Tanggula Mountains during the rainy season all the while, but increases with increasing latitude persistently from the Tanggula Mountains to the northern Tibetan Plateau because of the replenishment of vapor with the relative heavy stable isotopic compositions originating from the inner Plateau. The situation in the dry season is different: the mean δ18O values in precipitation decrease basically along the path from south to north. Generally, the mean δ18O in precipitation during the rainy season are lower than in the dry season for the regions controlled by the monsoons over South Asia or the Plateau, but contrary for the regions without monsoon or by weak monsoon.
出处
《地理科学》
CSCD
北大核心
2005年第2期190-196,共7页
Scientia Geographica Sinica
基金
国家自然科学基金资助项目(40271025)
湖南省教育厅研究项目(200203C210AA135360)
湖南师范大学重点建设学科项目。
关键词
稳定同位素
水汽路径
温度
降水量
stable isotope
vapor transport path
temperature
precipitation
